svn-gvsig-desktop / branches / v10 / libraries / libjni-proj4 / src / pj_deriv.c @ 40603
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/* dervative of (*P->fwd) projection */
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#ifndef lint
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static const char SCCSID[]="@(#)pj_deriv.c 4.4 93/06/12 GIE REL"; |
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#endif
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#define PJ_LIB__
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#include "projects.h" |
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int
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pj_deriv(LP lp, double h, PJ *P, struct DERIVS *der) { |
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XY t; |
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lp.lam += h; |
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lp.phi += h; |
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if (fabs(lp.phi) > HALFPI) return 1; |
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h += h; |
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t = (*P->fwd)(lp, P); |
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if (t.x == HUGE_VAL) return 1; |
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der->x_l = t.x; der->y_p = t.y; der->x_p = -t.x; der->y_l = -t.y; |
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lp.phi -= h; |
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if (fabs(lp.phi) > HALFPI) return 1; |
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t = (*P->fwd)(lp, P); |
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if (t.x == HUGE_VAL) return 1; |
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der->x_l += t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l -= t.y; |
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lp.lam -= h; |
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t = (*P->fwd)(lp, P); |
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if (t.x == HUGE_VAL) return 1; |
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der->x_l -= t.x; der->y_p -= t.y; der->x_p += t.x; der->y_l += t.y; |
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lp.phi += h; |
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t = (*P->fwd)(lp, P); |
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if (t.x == HUGE_VAL) return 1; |
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der->x_l -= t.x; der->y_p += t.y; der->x_p -= t.x; der->y_l += t.y; |
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der->x_l /= (h += h); |
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der->y_p /= h; |
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der->x_p /= h; |
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der->y_l /= h; |
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return 0; |
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} |